Semi-hydraulic lift and improved valve therefor

ABSTRACT

A low oil safety valve for use in semi-hydraulic lifts or hoists is disclosed herein. The improved valve includes a buoyant member that floats the valve in the lift hydraulic oil to hold the valve inoperative until the oil level in the lift drops below a predetermined, safe level. Attached to the lower end of the buoyant member is a seal member that includes an outer seal portion and an inner seal portion. The outer seal portion is engageable with the bottom plate of the lift plunger to prevent air and oil, when the oil level is below the predetermined safe level, from being discharged into the lift cylinder and thus causing erratic movement of the plunger. The inner seal portion encircles and sealingly engages an air line extending into the plunger to completely close the opening through the bottom plate of the hoist. The air line seal and the bottom plate seal are carried by the buoyant member, thus, both seals can be quickly and easily replaced without the necessity of removing the plunger from the cylinder as is usually necessary to replace the air line seal which is most often found in the bottom plate.

United States Patent 1 Davis 1 SEMI-HYDRAULIC LIFT AND IMPROVED VALVETHEREFOR [75] Inventor:

[52] US. Cl 91/4 A [51] Int. Cl FlSb 21/04 {58] Field of Search 91/4 A[56] References Cited UNITED STATES PATENTS 2,637,302 5/1953 Harrison etal. 91/4 A 2,970,577 2/1961 Sinclair 91/4 A 3,140,641 7/1964 Clark etal. 91/4 A 3,237,523 3/1966 Wallace 91/4 A 3,363,511 1/1968 Hott etal.... 91/4 A 3,435,731 4/1969 Browne 91/4 A Primary ExaminerPaul E.Maslousky Attorney- Robert W. Mayer, Roy L. VanWinkle et al.

[111 3,744,372 [451 July 10, 1973 [57} ABSTRACT A low oil safety valvefor use in semi-hydraulic lifts or hoists is disclosed herein. Theimproved valve includes a buoyant member that floats the valve in thelift hydraulic oil to hold the valve inoperative until the oil level inthe lift drops below a predetermined, safe level. Attached to the lowerend of the buoyant member is a seal member that includes an outer sealportion and an inner seal portion. The outer seal portion is engageablewith the bottom plate of the lift plunger to prevent air and oil, whenthe oil level is below the predetermined safe level, from beingdischarged into the lift cylinder and thus causing erratic movement ofthe plunger. The inner seal portion encircles and sealingly engages anair line extending into the plunger to completely close the openingthrough the bottom plate of the hoist. The air line seal and the bottomplate seal are carried by the buoyant member, thus, both seals can bequickly and easily replaced without the necessity of removing theplunger from the cylinder as is usually necessary to replace the airline seal which is most often found in the bottom plate.

7 Claims, 4 Drawing Figures PATENIE JUL 1 @1915 FIG. 3

PICS. 2

FIG.

SEMI-HYDRAULIC LIFT AND IMPROVED VALVE THEREFOR BACKGROUND OF THEINVENTION This invention relates generally to semi-hydraulic lifts orhoists. More particularly, but not by way of limitation, this inventionrelates to semi-hydraulic lifts for automotive vehicles that incorporatean improved low oil level safety valve.

The improved valve and hoist described hereinafter is an improvementover the valves and hoists shown and described in US. Pat. No. 3,140,641issued July 14, 1964 to J. E. Clarke, et al, U. S. Pat. No. 3,237,523,issued Mar. 1, 1961 to G. A. Wallace, and U. S. Pat. No. 3,453,731issued Apr. 1, 1969 to A. T. Browne.

Each of the aforesaid patents illustrates a hoist structure havingappropriate seals to provide both an outer seal for closing the openingthrough the bottom plate of the plunger and an inner seal that sealsagainst the air line. The problems encountered with such hoists haveprimarily involved the inner seal.

During the operation of lifts and hoists, and particularly when the oillevel is low, a very low hydrostatic head exists on the safety valveeven when the lower or outer seal portion is in sealing engagement withthe bottom plate of the plunger. Also, and even though some differentialin pressure is created due to the flow of air and liquid between the airline and the inner seal, the formation of a fluid-tight seal with theair line is very difficult due, at least in part, to the very low forcesavailable.

As will be appreciated by those skilled in the art, the attempt to forma fluid-tight seal between a smaller diameter member and a seal having alarger diameter than the diameter of the member results in the sealwrinkling or buckling as the seal collapses inwardly. A seal may beattained over the major portion of the surface area, but there areusually portions thereof wherein leakage occurs.

It is also necessary that the valve be free to float along the air lineas the liquid level changes in the plunger. Accordingly, the inner sealthat closely encircles the air line, must have a sufficiently largeinside diameter to permit such freedom of movement and, yet, must becapable of collapsing inwardly into tight sealing engaement with the airline.

It will be noted in the Browne patent, cited above, that the seal forthe air line is located in the bottom plate of the plunger and thesafety valve does not have to form a seal with the air line. With theseal located in this position, a fluid-tight seal can be attained andmaintained at all times. However, the telescoping action of the plungerwith respect to the air line exposes the seal to constant wear whichseverely reduces the life of the seal. The seal must be replaced fairlyoften and, since the seal is located at the bottom of the plunger, it isnecessary to remove the entire plunger from the 'liftcylinder in orderto accomplish the replacement. The expense and difficulties involved inreplacing a seal located in the bottom plate of the plunger areapparent.

Accordingly, it is one object of this invention to provide an improvedsemi-hydraulic lift that incorporates a buoyant low oil safety valvethat seals against the air line and bottom plate when the liquid levelis below a predetermined valve.

A further object of the invention is to provide an improved low oilsafety valve that effectively closes the opening extending through thebottom plate of the plunger and seals against the air line.

Still another object of the invention is to provide an improved low oilsafety valve for hydraulic lifts that is easy and inexpensive tomanufacture, requires little or no maintenance, and that can be quicklyand easily replaced when necessary.

SUMMARY OF THE INVENTION This invention contemplates an improvedsemihydraulic lift including a cylinder, an air line extendinglongitudinally within the cylinder and a plunger located within thecylinder encircling the air line. The plunger is moveable telescopicallywith respect to the air line and cylinder. A bottom plate on the plungeris normally immersed in a liquid and has an opening extendingtherethrough to receive the air line. An improved low level controlvalve is slidingly disposed on the air line within the plunger andincludes: a buoyant body encircling the air line and forming an annularspace with the air line; a resilient valve body attached to the buoyantbody and having an outer seal portion projecting relatively toward thebottom plate and an inner seal portion projecting lengthwise into theannular space. The inner seal portion encircles the air line and has athin, flexible cross-section and spaced notches in the end disposed inthe annular space to permit the inner seal portion to sealingly engagethe air line independently of the outer seal portion.

The foregoing and additional objects and advanages of the invention willbecome more apparent as the following detailed description is read inconjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view of animproved hoist constructed in accordance with the invention.

FIG. 2 is a cross-sectional view of the hoist of FIG. 1, butillustrating the hoist in a difierent operating position.

FIG. 3 is an enlarged cross-sectional view of a portion of the hoist ofFIG. 1 showing the low oil safety valve in detail.

FIG. 4 is a view similar to FIG. 3, but illustrating the valve of FIG. 3in another operating position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to thedrawing and to FIG. 1 in particular, shown therein and generallydesignated by the reference character 10 is a semi-hydraulic lift orhoist that is constructed in accordance with the invention. The hoist 10includes a cylinder 12 that is normally located in a pit (not shown) anddisposed in a substantially vertical position as illustrated.

The cylinder 12 has a closed lower end 14. An air line 16 is connectedto the lower end 14 of the cylinder 12 and extends therethrough into aplenum 18 mounted on the lower end 14 of the cylinder 12. The plenum 18is connected to a source of compressed air (not shown) by an air line20.

The air line 16 is disposed coaxially in the cylinder 12 and extendsupwardly to approximately the upper end 22 of the cylinder 12. The upperend 22 of the cylinder 12 includes appropriate bearings and seals 24 foroperably supporting a plunger 26 that is telescopically disposed withinthe cylinder 12.

The plunger 26 includes a top end closure 28 which may be removable orat least include a removable inspection opening for access to theinterior of the plunger 26. Also extending through the top closure 28 isan oil level gauge 30 which provides an indicia for assisting inmaintaining the oil level in the hoist at a predetermined level forsafely operating the hoist.

A bottom plate 32 on the plunger 26 has an opening 34 extendingtherethrough to receive the air line 16 and also to receive a deflectormember 36 which also encircles the air line 16. As may be seen moreclearly in FIG. 3, the opening 34 is sufficiently large to permit fluidflow therethrough even though both the deflector member 36 and the airline 16 are disposed therein.

To stabilize the plunger 26 in the cylinder 12, an annular bearing 38encircles the lower end of the plunger 26 and is disposed in slidingengagement with the interior wall of the cylinder 12. It should bepointed out that the plunger 26 will also carry, at its upper end, asuperstructure (not shown) that is appropriately arranged andconstructed to engage and lift a vehicle or to perform other servicesthat may be required of the hoist 10.

As previously mentioned, the air line 16 extends upwardly within theplunger 26 terminating in an abutment member 40 which provides a stop orupper limit for a low oil safety valve 42 that is slidingly disposed onthe air line 16.

As shown in FIG. 3, the deflector member 36 is located in the opening 34and has a diameter slightly smaller than the diameter of the opening 34to provide an annular space therethrough through which oil can flow asthe plunger 26 moves in the cylinder 12. The upper end of the deflectormember 36 is formed into a flange 44 that extends outwardly to adiameter larger than the diameter of the opening 34. Fluid flowingthrough the opening 34 is deflected to prevent the formation of bubbleswhich may cuase erratic operation of the hoist 10.

The low oil safety valve 42 includes a buoyant body 46 that encirclesthe air line 16 and forms an annular space 48 therewith. The buoyantbody 46 is to be constructed from a material that provides sufficientbuoyancy so that the valve 42 will float at or near the surface of theoil in the hoist 10.

A valve member 50 is attached to the lower end of the buoyant member 46and is constructed from a resilient material which is compatible withthe oil in the hoist. The valve member 50 includes a downwardlyprojecting, annular outer seal portion 52 that is arranged to sealinglyengage the bottom plate 32. The outer seal portion 52 has a diametersufficiently large to encircle the flange 44 of the deflector member 36and thus form a continuous seal with the surface of the bottom plate 32to close the opening 34. A radially extending flange portion 54 of thevalve member 50 connects the outer seal portion 52 with an inner sealportion 56 that projects upwardly into the annular spac 48 in thebuoyant body 46.

It will be noted that the inner seal portion 56 is of relatively thincross-section and has an inner diameter somewhat larger than the outerdiameter of the air line 16 so that the valve 42 is free to moverelative to the air line 16 as the oil level changes in the hoist 10.The upper end of the inner seal portion 56 is provided with a pluralityof spaced notches 58 to increase the flexibility of the inner sealportion 56 and to make it more responsive to the relatively small fluidhead that will be remaining in the annular space 48 when the oil levelis low. Also, the inner seal portion 56 must be sufficiently flexible tomove in response to the relatively small differential in pressure thatexists as oil passes downwardly through the space between the inner sealportion 56 and the air line 16.

As mentioned earlier, one of the difficulties in forming a seal with asmaller diameter member, such as the air line 16, has been the tendencyof the seal member which is larger in diameter, to buckle and thus forman imperfect seal. The notches 58 are provided so that as the sealportion 56 collapses inwardly, the inner surface thereof willcontinuously engage the exterior of the air line 16 and form afluid-tight seal therewith.

As an example of the structure and dimensions of the inner seal portion56, it has been found that with a cross-sectional thickness of 0.031 ofan inch and a heighth of 0.500 of an inch, notches 58 cut approximately0.375 of an inch deep and having a base dimen sion of 0.047 of an inchwill provide sufficient flexibility and permit sufficient collapse toprovide an effective seal between the inner seal portion 56 and the airline 16. It should, of course, be understood that these dimensions aregiven by way of example only and that reasonable variations therefromshould work equally well and are contemplated by the invention. The sizeand shape of the notches 58 will also vary with the hardness of thematerial utilized in forming the valve member 50.

OPERATION OF THE PREFERRED EMBODIMENT With the hoist 10 in the conditionillustrated in FIG. 1, air is introduced through the air line 20 intothe plenum 18 from which it passes into the air line 16 and outwardly ofthe upper end thereof. Oil contained within the plunger 26 is thenforced downwardly through the opening 34 into the interior of thecylinder 12.

As the oil is displaced out of the plunger 26, the plunger 26 begins torise as is illustrated in FIG. 2. The valve 42 floats near the surfaceof the oil and will continue to do so as the plunger 26 rises in thecylinder 12. In the event that there is not sufficient oil in theplunger 26 to permit the full extension of the plunger 26 relative tothe cylinder 12, the low oil safety valve 42 will move relativelydownwardly along the air line 16 with the oil level until the outer sealportion 52 thereon engages the bottom plate 32 as shown in FIG. 4. Whenthis occurs, oil is prevented from passing the outer seal 52 through theopening 34 and an increase in flow ve locity occurs between the innerseal portion 56 and the air line 16.

A force is exerted on the inner seal portion 56 both by the differentialin pressure due to the flow and also due to the slight head of fluidexisting in the annular space 48. The flexibility of the inner sealportion 56 and the notches 58 permit the inner seal portion 56 to moveinto sealing engagement with the air line 16 thereby preventing the flowof oil and air into the cylinder 12 and thus stopping the upwardmovement of the plunger 26 relative to the cylinder 12. It should alsobe noted that the configuration of the valve member 50 affords completeindependence of the inner and outer seal portions. That is, deformationor movement of the outer seal portion 52 is not necessary to permit theinner seal portion 56 to sealingly engage the air line 16. Thefluid-tight seals prevent erratic movement of the plunger 26 which canoccur if air is expelled from the plunger 26 into the cylinder 12instead of oil.

To lower the plunger 26, air pressure is released from the line whichpermits air to flow from the interior of the plunger 26 and outwardlythrough the air line 16. The valve 42 lifts off the bottom plate 32permitting oil to return from the cylinder 12 into the interior of theplunger 26 and the plunger 26 returns to the position illustrated inFIG. 1.

One highly desirable feature of the invention is that the seal betweenthe air line 16 and the valve 42 is carried by the valve 42 and thuswill be accessible from the upper end of the plunger 26. Thisarrangement avoids the necessity of removing the plunger 26 in the eventthat wear does occur on the seal portion 56. Since the seal portion 56is normally out of engagement with the air line 16, it is notcontemplated that the valve 42 will need to be replaced with any degreeof frequency.

It will be understood that the foregoing detailed description is but anexample of the invention and that many modifications and variations canbe made therein without departing from the spirit and scope of theinvention.

The invention is defined as follows:

1. in an improved semi-hydraulic lift, including a cylinder, an air lineextending longitudinally within the cylinder and a plunger locatedwithin the cylinder encircling the air line and moveable telescopicallywith respect to the air line and cylinder, the plunger having a bottomplate immersed in a liquid and an opening through the bottom plate toreceive the air line, and including an improved low level control valve,comprising:

a buoyant body encircling the air line within the plunger and forming anannular space with the air line; and,

a resilient valve body attached to said buoyant body and slidinglydisposed on the air line, said valve body including an outer sealportion projecting relatively toward the bottom plate and an inner sealportion projecting lengthwise into said annular space, said inner sealportion being disposed adjacent to the air line and having a thinflexible crosssection and spaced notches in the end disposed in saidannular space to permit movement of said inner seal portion into sealingengagement with the air line independently of said outer seal portion.

2. The improved semi-hydraulic lift of claim 1 wherein the notches insaid inner seal portion are triangular in configuration and have a basedimension slightly greater than the thickness of said end crosssectionand have a height about three-fourths of the length of said inner sealportion.

3. The improved semi-hydraulic lift of claim 1 wherein said inner sealportion is spaced from said buoyant body, whereby the liquid in saidannular space exerts a force on said inner seal portion when said outerseal portion is in engagement with the bottom plate, in a direction tomove said inner seal portion toward the air line.

4. An improved semi-hydraulic lift comprising:

a normally, vertically oriented cylinder at least partially filled witha liquid;

a hollow plunger located in said cylinder for telescoping movement, saidplunger having a bottom plate with an opening extending therethrough;

an air line connected to said cylinder and projecting through theopening into said plunger; and,

valve means slidingly located on said air line within said plunger, saidvalve means including a buoyant body encircling and forming an annularspace with said air line, and resilient valve body attached to saidbuoyant body, said valve body having an outer seal portion projectingtoward said bottom plate and being engageable therewith to close saidopening and an inner seal portion projecting into said annular space,said inner seal portion being disposed adjacent to said air line andhaving a thin, flexible cross-section and spaced notches in the enddisposed in said annular space to permit movement of said inner sealportion into sealing engagement with said air line independently of saidouter seal portion when said outer seal portion is in sealing engagementwith said bottom plate.

5. The improved lift of claim 4 wherein said outer seal portion isannular in configuration;

said inner seal portion is annular in configuration, spaced from saidouter seal portion and of smaller diameter than said outer seal portion;and,

a radially extending flange portion extending between the lower end ofsaid inner seal portion and the upper end of said outer seal portionretaining said seal portions in spaced relationship.

6. The improved lift of claim 5 and also including a deflector memberlocated in said opening and having a radially extending flange disposedwithin said plunger, said flange having an outer diameter sized to fitwithin said outer seal portion.

7. The improved semi-hydraulic lift of claim 6 wherein the notches insaid inner seal portion are triangular in configuration and have a basedimension slightly greater than the thickness of said end crosssectionand have a height about three-fourths of the length of said inner sealportion.

1. In an improved semi-hydraulic lift, including a cylinder, an air lineextending longitudinally within the cylinder and a plunger locatedwithin the cylinder encircling the air line and moveable telescopicallywith respect to the air line and cylinder, the plunger having a bottomplate immersed in a liquid and an opening through the bottom plate toreceive the air line, and including an improved low level control valve,comprising: a buoyant body encircling the air line within the plungerand forming an annular space with the air line; and, a resilient valvebody attached to said buoyant body and slidingly disposed on the airline, said valve body including an outer seal portion projectingrelatively toward the bottom plate and an inner seal portion projectinglengthwise into said annular space, said inner seal portion beingdisposed adjacent to the air line and having a thin flexiblecross-section and spaced notches in the end disposed in said annularspace to permit movement of said inner seal portion into sealingengagement with the air line independently of said outer seal portion.2. The improved semi-hydraulic lift of claim 1 wherein the notches insaid inner seal portion are triangular in configuration and have a basedimension slightly greater than the thickness of said end cross-sectionand have a height about three-fourths of the length of said inner sealportion.
 3. The improved semi-hydraulic lift of claim 1 wherein saidinner seal portion is spaced from said buoyant body, whereby the liquidin said annular space exerts a force on said inner seal portion whensaid outer seal portion is in engagement with the bottom plate, in adirection to move said inner seal portion toward the air line.
 4. Animproved semi-hydraulic lift comprising: a normally, vertically orientedcylinder at least partially filled with a liquid; a hollow plungerlocated in said cylinder for telescoping movement, said plunger having abottom plate with an opening extending therethrough; an air lineconnected to said cylinder and projecting through the opening into saidplunger; and, valve means slidingly located on said air line within saidplunger, said valve means including a buoyant body encircling andforming an annular space with said air line, and a resilient valve bodyattached to said buoyant body, said valve body having an outer sealportion projecting toward said bottom plate and being engageabletherewith to close said opening and an inner seal portion projectinginto said annular space, said inner seal portion being disposed adjacentto said air line and having a thin, flexible cross-section and spacednotches in the end disposed in said annular space to permit movement ofsaid inner seal portion into sealing engagement with said air lineindependently of said outer seal portion when said outer seal portion isin sealing engagement with said bottom plate.
 5. The improved lift ofclaim 4 wherein said outer seal portion is annular in configuration;said inner seal portion is annular in configuration, spaced from saidouter seal portion and of smaller diameter than said outer seal portion;and, a radially extending flange portion extending between the lower endof said inner seal portion and the upper end of said outer seal portionretaining said seal portions in spaced relationship.
 6. The improvedlift of claim 5 and also including a deflector member located in saidopening and having a radially extending flange disposed within saidplunger, said flanGe having an outer diameter sized to fit within saidouter seal portion.
 7. The improved semi-hydraulic lift of claim 6wherein the notches in said inner seal portion are triangular inconfiguration and have a base dimension slightly greater than thethickness of said end cross-section and have a height aboutthree-fourths of the length of said inner seal portion.